Diesel fuels



Patented F eb. 27, 1945 DIESEL FUELS I Thomas T. Noland and Edwin M.Nygaard, Woodbury, N.

J., assignors to Socony-Vacuum Oil Company, Incorporated, a corporationof New York No Drawing. Application March 31, 1943, Serial No. 481,290

15 Claims.

This invention has to do with fuels for internal combustion engines ofthe Diesel or compression ignition type, and, more particularly, has todo with the improvement of such fuels by the addition thereto of acharacterizing ingredient.

In order that the Diesel engine may be operated at maximum efiiciency,ignition of the fuel should be essentially instantaneous. Delayedignition or poor coordination between the combustion and cylinderconditions is the cause of knocking in Diesel engine operation. As iswell known to those familiar with the art, this condition may beremedied by adding small amounts of certain materials or compounds toDiesel or compression ignition fuels. Compounds possessed of suchcharacterizing ability accelerate the ignition of the fuel and, thus,provide a means whereby the ignition delay period of the fuel isrendered extremely short. In this way, the better grades of Diesel fuelsare enhanced and. low-grade hydrocarbon mixtures are so improved inignition quality that they may be used as fuels.

This invention is based upon the discovery that nitrolic acids andpseudonitroles are effective in improving the ignition quality of Dieselformulae: 1

Nlflollclclds Pseudonltrolcs NO: NO: a- =NOH R -e-m" wherein R is ahydrogen atom or a hydrocarbon radical, such as an alkyl, aryl,'aralkyl, or alkaryl radical; R and R" are hydrocarbon radicals. such asalkyl, aryl, aralkyLor alkaryl radicals and may be the same or differentradicals. Typical of the nitrolic acids are methyl, ethyl, propyl,phenylmethyl, and tolylmethyl nitrolic acids. Illustrativepseudonitroles are propyl, butyl. phenylmethyl, and xylylmethylpseudonitroles. Particular preference is given herein to propyl nitrolicacid and to propyl pseudonitrole.

The pseudonitroles represented by the .foregoing general formulaeapparently exist in a monomeric form and in a dimeric .form. Forexample, propyl pseudonitrole is a white solid in the dimeric form,whereas the monomer is a blue liquid. We, have found that the monomer ofpropyl pseudonitrole is more soluble than the dimer in a non-viscouspetroleum oil. We have also found that the more oil-soluble monomer canbe obtained substantially free of the dimer by using a hydrocarbon oildiluent-in the procedures referred to hereinafter. In this way, the

more desirable form of theDiesel fuel improving agents contemplatedherein, is obtained. It is to be understood, however, that both the moreoil-soluble monomeric forms and the less oilsoluble dimeric forms ofpseudonitroles are contemplated by the present invention.

Several 'methods of. preparation of nitrolic acids and pseudonitrolesare knownto those skilled in the art,

In general, these methods involve the reaction of a primary or asecondary nitro-parafl'in with nitrous acid at a temperature less thanabout 10 0. Detailed descriptions of such methods are provided in thechemical literature, as in Annalen 175, 114 (1875) and 175, (1875).Recently a novel procedure for the preparation of these compounds hasbeen developed. In this latter procedure, a nitrolic acid is preparedfrom a primary nitro'paraflin, aqueous alkali hydroxide and mineral acid(other than nitrous acid) at a temperature below about 10 C. Similarly,in this procedure, a pseudonitrole is obtained from a secondarynitroparaflln, said alkali and said acid at a temperature below about 10C. It will be apparent that while nitrous acid or alkali nitrite is notused in this recently. developed procedure, the equivalent of nitrousacid or alkali nitrite is formed therein and reacts. to introduce anitroso group (-N0) into the desired compounds. A

' As an example of the nitrolic acids, we have prepared propyl nitrolicacid by a method to that described in Annalen 175, 114 (1875) and toillustrate the poeudonitrols we have prepared propyl pseudonitrole by amethod similar to that described in Annalen 1'75, 120 (1875).

Exmu I Propyl nitrolic acid The reaction involved in the method ofpreparation described below is represented by the following Equation 1:

' Twenty-two grams (0.25 mole) of l-nitropro- I pane were placed in areaction flask equipped with a stirrer, thermometer and dropping funnel,and surrounded by an ice bath. A solution of sodium hydroxide, 110grams, was added slowly, care being taken to keep the temperature belowabout 10 C. After all of the l-nitropropane had dissolved in the alkalisolution, 20 grams of sodium nitrite were addedslowly to the solution.When the nitrite had dissolved therein, cold, dilute hydrochloric acidwas added dropwise to the solution at approximately 5 C. The reactionmixture turned dark red at first but became lighter in color as moreacid was added. Addition of acid required about 2 hours and wascontinued until the reaction mixture was light blue-green in color. Theblue-green reaction mixture was then made alkaline with dilute sodiumhydroxide solution and reacidified with dilute hydrochloric acid. Afterrepeating this lastmentioned operation three times, the slightly acidreaction mixture was extracted three times with successive portions (80cc. each) of ether. The ether extract thus obtained was filtered and theether allowed to evaporate spontaneously. Upon evaporation of the ether,propyl nitrolic acid was obtained as a mixture of white crystals (M. Pt.59-60 C.) and a yellow oil. The yield was grams or 51% of thetheoretical.

EXAMPLE. II

Prom l pseudonitrole The reaction between a secondary nitroparafiin, as2-nitropropane, and nitrous acid is represented by Equation II:

Twenty-five grams (0.36 mole) of 2-nitropropane were added slowly tosolution of '20 grams of potassium hydroxide in about 150 cc. of water.The mixture thus formed was kept in a tightly stoppered flask, which wasimmersed in an ice bath to prevent a rise in temperature. The flask wasshaken from time to time to aid in dissolving the nitro compound. Whenthe 2-nitropropane had dissolved, 21 grams of sodium nitrite were addedand dissolved. The solution was then poured into a flask equipped withstirrer, thermometer and dropping funnel. This flask was surrounded withan ice bath to maintain a low temperature within said flask.Concentrated sulfuric acid, 70 grams, diluted with ice water, was addedslowly at a temperature be low 10 C. As the acid was added, the solutionturned blue and a pale blue solid began to separate. When all of theacid had been added, the

solid was filtered off on a Buchnerfunnel, then washed with dilutepotassium hydroxide and finally with cold water. The pale blue solid,which was propyl pseudonitrole, was then dried and weighed.- The yieldwas 23 grams or 70% of the theoretical.

The effectiveness of the nitrolic acids and pseudonitroles in improvingthe ignition qualities of Diesel fuel is demonstrated by comparativetest results of a. fuel blank and of a fuel blend. The fuel used in thetests described hereinafter was a representative Diesel fuel known inthe art as a catalytically cracked number two The ignition quality ofthe fuel and fuel blend was determined by comparison with a standardreference fuel in a converted C. F. R. engine using the ignition delaymethod. The value obtained in this test is expressed as the cetanenumber which is the per cent by volume of cetane in alphamethylnaphthalene having the same combustion characteristics of the sampleunder test (Reference: Proc. Amer. Soc. Testing Materials, vol. 36, I,418 (1936)).

The results obtained in the foregoing tests with fuel blends containingsmall amounts of propyl nitrolic acid and of propyl pseudonitroie, bothof which are typical of the Diesel fuel improving agents contemplatedherein, are set forth in the table below:

Table Cona, Cetane Increase Compound blended with bme fuel wt. number inoctane per cent of blend number Propyl nitrolic acid... 2 37. 4 4. 4 D0l 37. l 4. 1 Propyi pseudonitrole- 1 37. 5 4. 5

For the purposes of this invention, the nitrolic acids and pseudonitrolerepresented by the general formula shown hereinabove may be used inamounts of from about 0.1 per cent to about 5.0 per cent.

It is to be understood that the foregoing examples are illustrative onlyand not to be conwherein R represents a radical selected from the grouconsisting of hydrogen, and alkyl, aryl, aralkyl and alkaryl radicals,and said pseudonitrole being represented by the general for mula N orwherein R and R" represented radicals selected from the group consistingof alkyl, aryl, aralkyl and alkaryl radicals.

2. An improved Diesel fuel comprising a nonviscous hydrocarbon oil andin admixture therewith a minor proportion, from about 0.1 per cent toabout 5.0 per cent, of a compound selectedfrom the group consisting of anitrolic acid and a pseudonitrole, said nitrolic acid being representedby the general formula N O: R-o=,NoH

wherein R represents a radical selected from the group consisting ofhydrogen, and alkyl, aryl, aralkyl and alkaryl radicals, and saidpseudonitrole being represented by the general formula N n NO wherein Rand R" represent radicalsselected from the group consisting of alkyl,aryl, aralkyl and alkaryl radicals.

3. An improved Diesel fuel comprising a nonviscous hydrocarbon oil andin admixture therewith a minor proportion, suflicient to improve theignition quality of the fuel, of a nitrolic acid represented by thegeneral formula wherein R represents a radical selected from the groupconsisting of hydrogen and alkyl, aryl, aralkyl and alkaryl radicals.

4. An improved Diesel fuel comprising a nonviscous hydrocarbon oil andin admixture therewith a minor proportion, from about 0.1 per cent toabout 5.0 per cent, of a nitrolic acid represented by the generalformula wherein R represents a radical selected from the groupconsisting of hydrogen and alkyl, aryl, aralkyl and alkaryl radicals.

5. An improved Diesel fuel comprising a nonviscous hydrocarbon oil andin admixture therewith a minor proportion, suflicient to improve theignition quality of the fuel, of a. pseudonitrole represented by thegeneral formula wherein R and R" represent radicals selected from thegroup consisting of alkyl, aryl, aralkyl to about 5.0 per cent, of apseudonitrole represented by the general formula wherein R" and R"represent radicals selected from the group consisting of alkyl, aryl,aralkyl and alkaryl radicals.

7. An improved Diesel fuel comprising a nonviscous hydrocarbon oil andin admixture therewith a minor proportion, suflicient to improve theignition quality of the fuel, of propyl nitrolic acid.

8. An improved Diesel fuel comprising a nonviscous hydrocarbon oil andin admixture therewith a minor proportion, from about 0.1 per cent toabout 5.0 per cent, of propyl nitrolic acid.

9. An improved Diesel fuel comprising a nonviscous hydrocarbon oil andin admixture therewith a minor proportion, sumcient to improve theignition quality of the fuel, of propyl pseudonitrole.

10. An improved Diesel fuel comprising a nonviscous hydrocarbon oil andin admixture therewith a minor proportion, from about 0.1 per cent toabout 5.0 per cent, of propyl pseudonitrole.

'11. The method of accelerating the ignition quality of a liquidhydrocarbon fuel in an engine where the fuel is injected into the enginecylinder and ignites spontaneously therein,

which comprises admixing-with the fuel prior to its ignition in thecylinder, a minor proportion.

of a compound selected from the group consisting of nitrolic acid and apseudonitrole, said nitrolic acid being represented by the generalformula wherein R represents a radical selected from the groupconsisting of hydrogen and alkyl, aryl, aralkyl and alkaryl radicals,and said pseudonitrole being represented by the general formula andalkaryl radicals.

12. The method of accelerating the ignition quality of a liquidhydrocarbon fuel in an engine where the fuel is injected into the enginecylinder and ignites spontaneously therein, which comprises admixingwith the fuel, prior to its ignition in the cylinder, a minor proportionof a nitrolic acid represented by the general formula I R- =NOH whereinR represents a radical selected from the group consisting of hydrogenand alkyl, aryl, aralkyl and alkaryl radicals.

13. The method of accelerating the ignition quality of a liquidhydrocarbon fuel in an engine where the fuel is injected into the enginecylinder and ignites spontaneously therein, which comprises admixingwith the fuel, prior to its ignition in the cylinder, 9. minorproportion of which. comprises admixing with the fuel, prior to itsignition in the cylinder, 9, minor proportion of propyl nitrolic acid.

15. The method of accelerating the ignition quality of a liquidhydrocarbon fuel in an enzine where the fuel is injected into the enginecylinder and ignites spontaneously therein, which comprises admixingwith the tuel, prior to its ignition in the cylinder, a minor proportion10 of propyi pseudonitrole.

THOMAS T. NOLAND. EDVIIN M. NYGAARD.

